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Compounds derived from cow’s milk may have a similar ability to the analgesic morphine to alter important biochemical processes implicated in autism including those affecting gene function. That was the finding from new research by Malav Trivedi and colleagues* based at Northeastern University in the United States and Ghent University in Belgium.

A laboratory based study looking at morphine and various food-derived morphine-like compounds – opioid peptides – extracted from foods containing gluten, the primary protein found in wheat and other cereal crops, or casein found in mammalian dairy sources, researchers examined the effects on cell lines. They concluded that the addition of opioid peptides to cells may interfere with the uptake of cysteine, an important precursor of the cellular antioxidant glutathione, something already quite consistently found to be perturbed in at least a subgroup of people on the autism spectrum. Researchers further demonstrated that opioid peptides derived from both cow and human milk may also have the ability to increase genome wide methylation levels in the transcription start site region “with a potency order similar to their inhibition of cysteine uptake” so potentially affecting gene functions.

Although still the source of discussion and debate in science and lay circles, the use of a gluten- and casein-free (GFCF) diet in cases of autism spectrum disorder (ASD) continues to enjoy some following. The experimental evidence for such an approach is still relatively weak. There is also a continued dearth of knowledge about why such an approach could affect the behavioural presentation of autism outside of the presence of comorbidities such as lactose intolerance or coeliac (celiac) disease appearing alongside cases of autism.

One of the earliest hypothesis put forward to attempt to explain the positive effects reported for some children and adults following a GFCF diet relied on the appearance of opioid peptides following the breakdown of gluten and casein. Coupled with reports of increased intestinal permeability – the so-called leaky gut – the suggestion was that a state of opioid excess allowed transport of these peptides into the central nervous system (CNS) to exert an effect. Other studies looking at the use of medications designed to block opioid receptors such as the drug naltrexone in case of autism to some extent corroborated the hypothesis.

The results from Trivedi and colleagues offer an alternative explanation for how foods containing casein may be implicated in other processes previously reported as being present in cases of autism. The idea that DNA methylation may also be affected by such food by-products also taps into the increasingly important area of autism research known as epigenetics, where changes to gene function rather than structural changes to the genome may be important.

The authors note however that their study requires further replication. Their focus on a particular cell line represents a preliminary examination of the effects of opioid peptides and may not necessarily translate into real effects in real people. They add however that their results “provide a novel antioxidant-based biochemical pathway linking gut and brain function via the diet” and source for further investigations.

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